create a real looking circular eddy like at the base of waterfalls?

I recently traveled some distance to acquire images of several well known waterfalls. The main waterfall I visited though was in such an active state (I assume because it recently rained) that unfortunately its eddy pool at the base wasn't there and really gives it a punch in photos. Here is a sample of what I'm talking about:

So, I basically have the waterfall and the water surrounding it. How would I go about adding a realistic looking eddy pool at the base similar to the above? I tried dragging a radial gradient across the water, but it still ends up too perfect no matter what I do. I tend to sell my images, so I can't just copy the pool from someone elses nor want to do that anyway.